Brainstem & Cerebellum (V) Flashcards
Name the major fossa, and in which fossa are the brainstem and cerebellum?
What is the name of the bone right in front of the brainstem?
- The cranial fossa: anterior fossa, middle fossa and posterior fossa.
- The brainstem and cerebellum are in the posterior cranial fossa.
- bone in front of brainstem = clivius
https://courses.lumenlearning.com/suny-ap1/chapter/the-skull/
What do we call the dura mater extension that forms a lamina, indicating the division between cerebellum and the rest of the brain (a space called…?)?
And what sinuses surround this lamina?
- This lamina is the cerebellar tentorium.
- It defines the space bellow (cerebellar) as “infratentorial” and the space above as “supratentorium”
- down the middle of the tentorium cerebelli, we have the straight sinus, that, looking at it from a medial section, is at an angle, like the cerebellum.
- Passing round the two sides, to the front, are the transverse sinuses.
- the extension of the transverse sinuses that “closes” the tentorium cerebelli are the superior petrous sinuses
Name some important foramens in the base of the skull - what are they for?
Why? So cranial nerves can exit.
* foramen magnum: spinal cord
* jugular foramen: the jugular nerves
* optic canal foramen
two horizontal and vertical divisions of brainstem?
Horizontal:
* mesencephalon
* pons
* medulla
Vertical:
* basis
* tegmentum
* tectum
**what are the basis, tegmentum, and tectum ** in the 1) mesencephalon, 2) pons 3) medulla
In the** mesencephalon**:
* the basis = the cerebral peduncles
* tegmentum = several nuclei serving as a pathway for ascending and descending tracts, reticular formation, cranial nerves nuclei
* tectum: superior colliculi (visual processing & reflexive eye movements), inferior colliculi (auditory processing)
In the pons:
* basis = white matter tracts
* tegmentum = everal nuclei serving as a pathway for ascending and descending tracts, reticular formation, cranial nerves nuclei
* tectum: it’s the 4th ventricle
In the medulla:
* basis = pyramids
* tegmentum = nuclei as above
* tectum = none
What do we find in the brainstem?
- at the basis: descending motor pathways
- at the level of tegmentum: ascending sensory pathways, brainstem motor nuclei (origins) for brainstem tracts e.g., tectospinal,m rubrospinal, olivo-spinal , reticular formation + cranial nuclei for cranial nerves (from where they have afferents and efferents)
- tectum: superior & inferior colliculi
- decussations at the level of the pyramids
Where are the superior and inferior olives and what do they do?
**superior olive **= in the pons, plays a role in auditory pathway - sound localisation. They have coincidence detectors (specialised neurons) that detect differences in sound arrival between two ears.
* inferior olive: lower, in the medulla oblongata. The primary function = motor coordination & learning - provides cerebellar input. It sends climbing fibers, which are a type of excitatory axon, to the cerebellum.
Name at least 6 of the 12 cranial nerves in the picture in the link
https://www.exploringnature.org/db/view/Cranial-Nerves-Labeling-Page
[https://faculty.washington.edu/chudler/cranial.html]
Mneumonic:
” Oh, Oh, Oh, To Touch And Feel Very Good Velvet, such-A Heaven””
Olfactory nerve (CN I), optic nerve (CN II), oculomotor nerve (CN III), trochlear nerve (CN IV), trigeminal nerve (CN V), abducens nerve (CN VI), facial nerve (CN VII), vestibulocochlear nerve (CN VIII), glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), and hypoglossal nerve (CN XII).
What type of nerve (sesnory, motor, mixed) are the 12 cranial nerves below:
olfactory nerve
optic nerve
oculomotor nerve
trochlear nerve
trigeminal nerve
abducens nerve
facial nerve
vestibulocochlear nerve
glossopharyngeal nerve
vagus nerve
accessory nerve
hypoglossal nerve
- olfactory nerve: sensory
- optic nerve: sensory
- oculomotor nerve: motor (eye and pupil movement)
- trochlear nerve: motor (eye movement)
- trigeminal nerve: mixed - all facial info. Chewing, pain, touch
- abducens nerve: motor -eye movement
- facial nerve: mixed. Taste, ear movement, muscles used in facial expression.
- vestibulocochlear nerve: sensory - Hearing; balance
- glossopharyngeal nerve - mixed - taste; Somatosensory information from tongue, tonsil, pharynx; controls some muscles used in swallowing.
- vagus nerve: mixed. sensory, motor and autonomic functions of viscera (glands, digestion, heart rate)
- accessory/vagus nerve - motor - neck muscles
- hypoglossal nerve - motor - tongue
Where are the cranial nerve nuclei?
in the tegmentum
what are the cranial nerves poking out from below the colliculi?
trochlear nerves
what’s wrapped around the thalamus?
from inside to out:
thalamus –> internal capsule (WM) -> globus pallidus (GM) -> putamen (GM) -> caudate nucleus (GM) –> claustrum (thin sheet of GM, densely packed neurons) -> extreme capsule (WM) –> external capsule (WM) -> insular cortex –> opercula (GM) –> lateral sulcus
**Will the affected areas be affected ipsilaterally or contralaterally when LATERALLY LESIONING THE BRAINSTEM: **
- pyramidal (corticospinal) motor pathway & motor functioning
- cranial nerves and related areas of the head
- pain and temperature sensing
- proprioception and fine touch sensing
- Since the corticospinal tracts decussate in the medulla at the base of the pyramids, lesioning above this region will mean that the **opposite side of the body will be affected by motor deficits **(since they should be projecting there after decussating).
- Since the cranial nuclei & nerves are **ipsilateral ** to the side of the head being innervated, the same side of the head will be affected.
- Since pain and temp sensation - the** spinothalamic pathway** - decussates AS SOON as it enters the spinal cord, if we lesion the brainstem it will affect the sensation **contralaterally. **
- For the proprioception - the dorsal medial lemniscus pathway - since it decussates in the lower medulla (specifically, gracile and cuneate nucleus) but higher than the pyramidal decussation, how the sensations are affected by the lesion depend on how high or low the lesion is. if the lesion is higher than the lower medulla, pain & temp sensation will be disturbed contralaterally (other side of lesion). But if the lesion is lower than the medulla, because it’s lower than the decussation, it will result in ipsilateral deficits (same side as lesion).
imp: where does the dorsal medium lemniscus pathway (proprioception, fine touch) decussate?
lower medulla, specifically at the gracile and cuneate nuclei, which are a bit higher than the pyramidal decussations.
at the level of the medulla, where are the pain pathway tracts on a medial slice?
laterally
